The figure shows how to couple two TTL circuits using an optical coupler to obtain isolation. The circuit is shown in the August 1992 issue of Radio Electronics magazine.
This instrumentation amplifier with differential inputs was found in documentation from the 90s....
This circuit is from a Radio Electronics magazine from December 1958. The indicator instrument is analog...
Found in a 90s 303 Circuits, this circuit has an output power of 100 mW. L1 consists of 890 turns...